Electromagnetic vibrator



1 1950 D. s. SCHREIBER 2,533,595

. ELECTROMAGNETIC VIBRATORY Filed Dec. 18, 1945 2 Sheets-Shet 1 m nt 5 .3.

'0 n zime 1950 D. s. SCHREIBER 2,533,695

ELECTROMAGNETIC VIBRATOR Filed Dec. 18, 1945 2 Sheets-Sheet 2 {crew Patented Dec. 12, l950 ELECTROMAGNETIC VIBRATOR Dag Sigurdsson SchreiberjLidingo, Sweden, as-

signor to AB W. Dan Bergman, Sodertalje, Sweden, a joint-stock company of Sweden Application December 18, 1945, Serial No. 635,802

' In Sweden January 31, 1945 The present invention relates to an electromagnetic vibrator device for direct current, in which an armature in the form of a contact spring or the like is maintained in continuous oscillation by means of one or more electromagnets and automatic interrupters and thereby is caused to close and break contacts, which for example are used for converting direct current into alternate current or vice versa. Vibrators of this kind have relatively great internal losses, and therefore their efliciency is low when converting small powers. v

The object of the invention is to make a vibrator device, which has considerably lower internal losses at the same working conditions in other i respects, which according to the invention is'ob-.

tained thereby, that the driving magnet ispolarized and that the circuit includes a condenser, which is connected to coact-with the coil of' the driving magnet in such a way that" the alternating where his a constant.

The invention is illustrated by way of an example in the accompanying drawing, in which. Fig. 1 shows a plan view of a simple vibrator device according to the invention,

Fig. 2 shows a circuit diagram for a constructional form of a vibrator device according to the invention,

Figs. 3, 4 and show different diagrams, viz. Fig. 3 the current in the coil of the driving magnet, Fig. 4 the attracting magnetic force on the armature when using an unpolarized magnet, and Fig. 5 the alternating component of the magnetic force on the armature, when a polarized magnet is used according to the invention, all these .diagrams being shown as functions of time.

F18. 1 shows a preferred form of the vibrator device according to the invention. I is a barshaped permanent magnet. The angle-shaped poleshoe 4' is provided with a coil 2. An armature 3 carried by a leaf spring 6 is arranged to oscillate before; the pole shoes 4, 4', provided at the free ends of. the magnet poles. The said pole shoes I, 4' have recesse 5 of such form as to 4 Claims. (01. 318129) cause the magnetic force acting upon the arma ture 3'to increase in a desired manner with the amplitudeof oscillation. The spring 6 carrying the'a'rmature 3 is so dimensioned that it is stiff enough to prevent the armature from impinging upon the poleshoes 4, 4'. A contact I mounted on the spring 6 coacts with a fixed contact 8. When the vibrator is at rest, i. e. with no current in coil 2, the direction of the force exerted by spring 6 on armature 3 is such as to pull the latter away from the pole pieces 4, 4 but armature movement isprevented by a substantially equal pull on the armature in the opposite direction due to the magnetic attractive force set up across the pole pieces 4-4 by the permanent magnet I which thus leaves the armature in a state of stable equilibrium with contacts I and 8 closed. When current is applied to coil 2, the flux produced thereby is in such direction as to aid" thefiux produced by magnet I and hence armature 3 is caused to move in the direction of the pole pieces 44' whereupon contacts I and 8 becom momentarily separated. I -Fig.2' shows a circuit diagram of a suitable constructional form of the device according to the invention. The parts corresponding to the parts shown in Fig. 1 have the same reference numerals as in Fig. 1. The driving coil- 2 is-fed from a directcurrent battery 9, and a condenser 10 is connected across the contacts 1, 8.

The mode of operation of the device according to the invention as compared with that of a vibrator having an unpolarized magnet and without condenser will be seen in Figs. 3-5. The upper curves of these figures show'the conditions in-a device withoutcondenser in the circuit, and the bottom curves show the conditions in a device with a condenser, which is so dimensioned that the oscillatory circuit consisting of the condenser and the coil of the driving magnet is approximately in resonance with the mechanical natural frequence of the armature. As already mentioned, Fig. 3 shows the variation of the current when using a polarized as well as an unpolarized magnet, Fig. 4 shows the attracting force when an unpolarized magnet is used and Fig. 5 the magnetic attracting force component due to the coil current when a polarized magnet is used. The bottom curve in Fig. 4' shows how the attracting force on the armature, when an unpolarized magnet is used, counteracts the returning movement of the armature during the currentfree period, while accordingto the bottom curve in Fig. 5, when a polarized magnet is used, the alternating component of the magnetic force on the armature which as explained above is the force due to the coil current alone acts all the time in the direction of motion of the armature. The result thereof is that the armature of the polarized vibrator has a considerably greater amplitude of oscillation and contact pressure than that of an unpolarized vibrator, when the conditions are the same in other respects.

Some data with respect to the internal losses of vibrators may be mentioned by way of examples. A normal vibrator for the conversion of direct current into alternating current, e. g. in an automobile radio, has a loss of about ,1 watt. A special construction of an unpo'larized vibrator has a loss of about 0.3 watt, while a polarized vibrator accordin to the invention has only a loss of 0.02 watt at the same contact pressure and breaking distance.

The best results are obtained, as already mentioned, if the condenser is so dimensioned that the oscillatory circuit consisting of the condenser and the coil of the driving magnet :is approximately .in resonance with the mechanical natural frequency of the armature, though satisfactory results will also :be obtained when using a somewhat greater condenser, but a smaller one should'not be used. Instead of connecting the condenser across the contacts it may also be connected across the magnet coil. If the vibrator is to beuserl in converters, the armature is, of course, provided with the necessary contact groups in addition to those required .for the automatic interruption.

The device according to the invention is not limited to the constructional form described and shown in the drawing but may be modified in many ways regarding its details without going beyond the scope of the invention.

.' Having now described my invention, what 'I claim as new and desire to secure by Letters 'Patent'fist:

.1. An electromagnetic vibrator adapted to be operated from a source of direct current'comprising a magnetic core having a pair .of juxtapose'd pole pieces and a permanent magnet section for' polarizing the same, a spring mounted armature disposed adjacent said pole pieces for motion relative thereto, a drivercoil surrounding said core, a set of contacts periodically opened and closed upon movement :of said armature and through which contacts said coil is connected tot'he source, and a condenser connected in circuit with said coil, said coil and condenser forming an oscillatory circuit having a resonant fre-.

quency substantially equal to the mechanical natural frequency of said spring mounted armature.

section to polarize the same, a cantilever spring mounted armature disposed adjacent said pole pieces for motion relative thereto, a driver coll surrounding said core, a set of contacts periodically opened and closed upon movement of said armature and through which contacts said coil is connected to the source; and a condenser connected in. circuit with said coil, said coil and condenser forming an oscillatory circuit having a resonant frequency substantially equal to the mechanical natural frequency of said spring mounted armature.

3. An electromagnetic vibrator device adapted to be operated from a source of direct current comprising, :a core having an air gap, a spring carried armature mounted for vibratory movement in said air gap relative to said core, means establishing a polarizing magnetic flux through said core and air gap, a driver coil surrounding said core, a set of contacts periodically opened and closed upon movement of said-armature and through which contacts said coil is period:

ically connected to the source, :and .a condenser connected in'circui-t with said coil, said coil and condenser forming an oscillatory, circuit a resonant frequency substantially equal to the mechanical natural frequency of said spring armature.

4. electromagnetic vibrator device dapted to be operated from a sourcecf direct current comprising, a core havingan airsgazp, ,aspring carried armature mounted for vibratory mover ment in said air gap relative to said :core, permanent magnet means establishing a polarizing magneticilux through said core and air gap. a driver coil surrounding said core, a setsoif contacts periodicallyopened and closed upon movement of said armature and through which con;- tacts said coil is periodically connected to source, and a condenser connected ,in circuit with said coil, said coil and condenser forming an oscillatory circuit having .a resonantfreiquency substantially equal to the mechanical natural frequency of said spring and armature.

DAG SIG-URDSSON SGHREIBER.

REFERENCES CITED The following references are :of record the file of this patent: 

